When you're outside, look around the area for a security bot named Victor. This is actually an optional part of the other quest you can currently do (They Went That-a-way). In any case, head into the Prospector Saloon to the northeast.

Inside, Sunny Smiles almost immediately approaches you and tells you to meet her outside. Snatch the {FIXIN' THINGS} skill magazine from the cabinet with the world globe if you'd like, although you'll lose some karma. Stealing things is best done when no one's around, and crouching also makes it less likely to get caught. You can also steal a {.357 MAGNUM REVOLVER} behind the bar, or even open the cash register for a quick buck. From now on, items denoted with {} brackets indicate a stealing procedure. Follow Sunny to the back and approach her (she's standing towards the northwest). She'll then hand you a [VARMINT RIFLE] and [5.56MM AMMO x30]. Shoot three sarsaparilla bottles from the fence and Sunny will ask you to join her and waste some Geckos. You can either end the tutorial, or join her.

Learning to use your rifle

KILLING GECKO'S

Follow Sunny south, then crouch when you're approaching the geckos. Sneak as close as possible to the windmill, then enter VATS (or not) and waste the two geckos. If you've lost any HP, drink from the clean water to replenish your health. Geckos can often be looted for gecko meat and/or gecko hides, so always search bodies, including animal corpses. Report back to Sunny and she'll once again give you the option to kill more geckos. After accepting, she hands you an additional [5.56MM AMMO x60]. Not too shabby!

Follow Sunny to the other wells and kill the remaining geckos. Talk to Sunny for your reward: 50 Bottle Caps. She's still got more to teach you, though! Accept and you'll start the 'By a Campfire on the Trail' quest.